National Institute of Environmental Health Sciences

Tuff Stuff Riddles Return to Brainteasers Index Return to NIEHS Kids' Pages Index

"Pre-School" Test for you:
Which way is the bus below traveling...toward the left or the right?

Can't make up your mind? Look carefully at the picture again. Pre-schoolers all over the United States were shown this picture and asked the same question, and 90% of them gave the correct answer!

You must cut a gold chain to pay someone for 7 days of service. The chain has 7 links on it, and you agree on a price of one link per day. The employee will not work without receiving that day's pay each afternoon, but you do not wish to give him more than his daily payment for the fear that he will not return. Therefore, you must cut some of the links on the chain to make the daily payments. What is the smallest number of links you need to cut so that the employee receives only one link each day?

While driving home after a hard day's work, I came upon the following problem. An entire town had been painted black; the roads, pavements, buildings, hedges, and everything that did not move had been painted black. In addition, my vehicle's headlights were not working, no moon was visible, and power was off in the area, so there were no street or house lights around. At that moment, I entered a curve where a solid black dog (deaf, and thus unaware of the approaching car) was sitting in the road. He had his back to me, so there was not even a glint in his eye, yet I was able to swerve round him quite easily and without danger. How was this achieved?

A man has an acreage where grass grows continuously and evenly. If 20 cows eat all the grass in 96 days and 30 cows eat all of the grass in 60 days, then how long does it take 70 cows to eat all of the grass?

You have three houses or squares drawn on paper, and below them three smaller squares representing gas, water, and electric service. Can you draw a line to get each utility into each house (9 total lines) without crossing over any line, changing the size of some of the houses, or going through one house to reach another?

Answer No -- the statement 'drawn on paper' implies that this is a 2D surface, and in two dimensions the problem has no solution. The best result you may get using the drawing above is only eight proper connections. But in three dimensions, the problem can pretty easily be solved. There is a real lesson in geometry here -- whether the six objects with connections are houses or just geometric points, the true answer is that one cannot make the nine connections on a two-dimensional surface without one of the lines crossing. Adding size to the houses and/or running lines through the houses, etc., simply avoids the problem by just changing the rules, rather than finding the true solution. One of the lessons, particularly in mathematics, is to discover what is impossible and thus can be excluded in solutions of other problems. The answer is not always to hammer the problem into a different one that looks solvable.

Good at math? Try this one.... 1=3
2=3
3=5
4=4
5=4
6=3
7=5
8=5
9=4
10=3

So what does
11=?
12=?
Answer11=6 and 12=6 (the number of letters in the number's name)

What do these words have in common: age, blame, curb, dance, evidence, fence, gleam, harm, interest, jam, kiss, latch, motion, nest, order, part, quiz, rest, signal, trust, use, view, win, x-ray, yield, zone?

AnswerAll the words can be used as both nouns and verbs.

What are the science teacher's favorite states?

AnswerSolid, liquid, and gas...the states of matter!

Answer Although there may be other solutions, here is a simple one: The first person takes his monthly salary (lets say $100), adds an arbitrary amount that only he knows (lets say $475) and whispers that number ($575) to the second person. The second person then adds his monthly salary (lets say $150) to that value and whispers the new total ($725) to the third person. The third person adds in his salary, whispers the new total to the fourth person and so on until the tenth person adds in his salary and whispers the final total to the first person. The first person then subtracts his arbitrary number from that total, divides by 10, which produces (assuming that no one made an error in arithmetic!) the average monthly salary for the group without anyone having to divulge their salary to anyone else.

What is the fastest time that a group of four people can row to the other side of the river with the following rules in place?

• The speed of the rowers is as follows:
  • Rower #1 -- rows in 1 minute
  • Rower #2 -- rows in 2 minutes
  • Rower #5 -- rows in 5 minutes
  • Rower #10 -- rows in 10 minutes
• All four people must get to the other side of the river using the rowboat
• Only two people can travel in, on, or around the boat at any one time.
• The person in the boat who rows at the slowest speed must do the rowing (they travel at the speed of the slowest person).

Answer 1) #2 rows #1 across in 2 minutes 2) #1 returns in 1 minute/option> 3) #10 rows #5 across in 10 minutes 4) #2 returns in 2 minutes 5) #2 rows #1 across in 2 minutes Total is 17 minutes, and steps 2) and 4) can be interchanged. The key is to have #10 row #5 across and have a faster rower waiting on the other side to take the boat back.


Four men are standing in a line as shown above and they cannot turn their heads. There is a brick wall between A and B that they cannot see through. They know that they each have one hat, and that of the four hats two are black and two are white. They cannot see the color of the hat that they are wearing. In order to be released from the line, they must call out the color of their hat. If they are wrong, no one can leave. They are not allowed to talk to each other, and they have been given ten minutes to figure out their hat color. After 1 minute:

• One of them calls out -- which one called out?
• How can he be 100% certain of the color of his hat?

This is not a trick question and there are no outside influences nor any other ways of communicating. They cannot move or see behind them, nor can they see through the wall. Answer C would call out, because he would know that if his hat were the same color as B's hat, then D would have known that his own hat was the opposite color of B and C's hat and would have called out. Since D did not speak then C knows that his hat is the opposite color of B's.

In a recent random drawing of three digits, the number 361 was drawn; immediately afterward in a random drawing of four digits, 2401 was drawn. Both of these numbers have something unusual in common -- what is it? And what are the chances of this happening again, remembering that in a random drawing numbers can begin with one or more zeroes. AnswerBoth numbers are perfect squares (19 squared and 49 squared) The three number drawing has exactly 1000 possible outcomes (000-999) The four number drawing has exactly 10,000 possible outcomes (0000-9999). To see how many squares are possible,take the square root of the maximum number and "round up"(to count the 000, which is a perfect square). Thus, since the square root of 999 is 31.6, there are 32 possible squares in the three number drawing (the squares of 0 through 31). Similarly, for the four number drawing, there are 100 possible squares (the squares of 0 through 99). Thus, the likelihood of both numbers being a squared number is (32/1000) x (100/10000) or 0.00032 (a little over 3 chances in 10,000).

Two postmen meet on their routes and they start talking.
Postman A says: "I know you have 3 sons, how old are they?"
Postman B says: "If you take their ages in years, and multiply them together, the result is your age."
A: "That`s not enough info"
B: "The sum of the 3 numbers equals the number of windows in that
building over there."
A: "Hmm... that`s still not enough."
B: "My middle son is red-haired."
A: "Ah, now I see!"
How old are the 3 sons?

Answer Answer and Explanation for Solution: With a little bit of work, you can discover that only one solution is possible: the kids must be 1, 5, and 8 because a solution with the same A and B involving twins (2, 2, and 10) is ruled out by the middle son with red hair. The product of both are 40 and the sums are 14. The basis for that solution is as follows: The postman's first statement tells us that x*y*z = A; the postman's second statement tells us that x+y+z = B; and the third statement tells us that x does not equal y does not equal z. We know that the three ages are different because the "middle" son has red hair, which implies that none of the children are twins. The most important piece of information in the puzzle is that there must be at least two sets of numbers that add together to give the same sum and multiply together to give the same product -- or he would have been able to figure it out without the third parameter about the middle child (no twins). Thus, there are two sets of three numbers x1, y1, & z1 and x2, y2, & z2 where x1 + y1 + z1 = x2 + y2 + z2 and x1 * y1 * z1 = x2 * y2 * z2 . It is not the fact that there are no twins, but the fact that the postman could NOT figure out the answer UNTIL he knew that there were no twins that is essential. He needed toknow that fact in order to solve the problem, and there must be only two different sets of age choices for the kids (one with twins; one without twins) that produce equivalent A's and B's.
Need a more detailed explanation?

A man is asked what his daughters look like. He answers, "They are all blondes, but two, all brunettes, but two, and all redheads, but two." How many daughters did he have?
AnswerThree: one blonde, one brunette and one redhead.

An old man said to a young man, "I have a daughter. She has as many brothers as she has sisters. Each one of her brothers has twice as many sisters as he has brothers. How many sons and daughters do I have?"
Answer 3 sons and 4 daughters (total of 7 sons and daughters) The answer to this problem can be found with a little algebra. Let S be the number of sons and D be the number of daughters. From the first statement we have: S=(D-1). From the second statement we have: 2(S-1) = D Solving for S and D gives S=3, D=4, i.e., 4 daughters and 3 sons.

The "he" puzzle:
Name an English word of more than 2 letters that both begins and ends with the letters 'he' (in that order). (Actually, there are two possible correct answers -- and "hehe" is not an acceptable solution.)
Answer Headache Or heartache

Pill Puzzler
You've been placed on a course of expensive medication in which you are to take one tablet of medicine A and one tablet of medicine B daily. You must be careful that you take just one of each because taking more of either can have serious side effects. Taking an A without taking a B, or vice versa, can also be very serious, because they must be taken together in order to be effective. In summary, you must take exactly one of the A pills and one of the B pills at one time. Therefore, you open up the A bottle, and you tap one A pill into your hand. You put that bottle aside and you open the B bottle. You do the same, but by mistake, two Bs fall into your hand with the A pill. Now, here's the problem. You weren't watching your hand as the pills fell into it, so you can't tell the A pill apart from the two B pills. The pills look identical. They are the same size, same weight, same color, same everything, and they are not marked differently in any way. What are you going to do? You cannot tell which pill is which, and they cost $100 a piece, so you cannot afford to throw them away and start over again. How do you get your daily dose of exactly one A and exactly one B without wasting any of the pills?
(speaking of throwing things away, don't miss our Reduce, Reuse, and Recycle tips!)
Answer CUT EACH OF THE THREE PILLS IN HALF, AND CAREFULLY SEPARATE THEM INTO TWO PILES, WITH HALF OF EACH PILL IN EACH PILE. You do not know which pill is which, but you are 100% sure that each of the two piles now contains two halves of pill B and half of pill A. Now go back into the pill A box, take out a pill, cut it in half, and add one half to each stack. Now you have two stacks, each one containing two halves of pill A, and two halves of pill B. Take one stack of pills today,and save the second stack for tomorrow. And the problem is solved."

Voiceless it cries
wingless flutters
toothless bites
mouthless mutters
Answer The wind

It cannot be seen,cannot be felt
cannot be heard, cannot be smelt
it lies behind stars and under hills
and empty holes it fills
Answer Darkness

Alive without breath,
as cold as death,
never thirsty,
ever drinking,
when tired, never winking.
Answer Fish



Dies half its life
lives the rest
dances without music
breathes without breath
Answer Trees

I live above a star, and yet I never burn,
I have eleven neighbors, and yet none of them turn,
I am visited in sequence, first, last or in between,
PRS (& sometimes Q)are my initials, now tell me what I mean.
Answer The "7" key on a telephone keypad. (Note: Newer phones have added the letter "Q" to the initials.)

What is better than the best, more evil than demons, the poor have it and the rich need it, and if you eat it, you will die?
Answer Nothing

I am one simple word, but I mean different things
One of my meanings brings great forceful swings,
The other of me, may have curve, like the first...
But only one meaning can help quench a thirst.
One of my meanings will often bring cheers,
Either of them could hold a few beers.
Answer A pitcher.

As I watch I see the world pass me by.
All the good, the bad, in the twinkle of an eye.
I watch and wait, and patiently sit.
I never began, so I shall never quit.
My only presence is in my being.
It is hardly noticed, and not worth a thing.
I'm fast as light, thin as air.
Run if you can. Run if you dare.
To avoid me is the mark of a fool.
For all you're worth, your life is my tool.
Though concealed, I am not shy.
The question is: What am I?
Answer I can see you're confused by my little rhyme. Don't fret, my friend. You have plenty of TIME! (An original poem/riddle Contributed by Kaaljmirek Kahlia)

What unusual property do the words FLOUR, TERN, and THIRSTY have in common? Answer Remove one letter from each word and they all spell a numeral. Four, Ten, and Thirty

Here's an original brainteaser submitted by an NIEHS scientist:
What six letter word in the English language contains ten other words without rearranging any of its letters?
Answer The word is "spared". The other words in it are: spa; spar; spare; pa (as in ma and pa); par; pare; pared; are; re (as in do-re-me); and red.

On that same order, what seven letter word in the English language contains ten other words without rearranging any of its letters.
Answer The word is "therein" The words are: the, there, he, re (as in do, re, mi), in, rein, her, here, ere, herein

You have two fuses (a fuse is something you burn to eventually set off an explosive), one which burns 1 hour and one which burns 2 hours. The fuses do not burn at a constant rate, so, for example, the last few inches of the first fuse could take 5 minutes or 55 minutes to burn. You have as many matches as you want. With these fuses, you have to measure a time period of exactly 45 minutes. How do you do this?
Answer First light the fuse of 1 hour AT BOTH SIDES AND simultaneously light the fuse of 2 hours AT ONE SIDE The first fuse will be gone in 0.5 hours. At that time, you light the second end of the fuse of 2 hours: 1.5 hours remain on this fuse. This fuse will now burn in exactly 45 minutes

You have a rope that will reach around the earth (+/- 40,000 km). If you put sticks of 1 meter high around the world and lay the rope on these sticks, how much longer will the rope need to be?
Answer ONLY 6.28 meter (= 2 PI) And the strange thing is that it even doesn't matter how great the original circle is: it can be 1m, 100m or 1000 km in radius, if you extend the radius by 1 meter, the rope always gets 6.28 meters longer.

Problems in the Elevator: A person lives on the tenth floor of a building. Every day he takes the elevator to go down to the ground floor to go out. When he returns he takes the elevator to the seventh floor and walks up the stairs to reach his apartment on the tenth floor. Only on rainy days does he take the elevator to the tenth floor. He hates the stairs, so why does he do it?
--- Answer --- ================================ He is a young man who cannot yet reach higher than the button for the 7th floor. But on rainy days, he can use his umbrella!

You have four unmarked bottles of pills each containing 100 tablets. One bottle of pills is poisoned. The good pills weigh exactly 1 gram a piece. The poisoned ones weigh exactly 1.1 gram a piece. You also have use of a scale, but can only use it one time. How can you determine with certainty which bottle of pills is poisoned? Answer (1) Remove 1 pill from Bottle 1. (2) Remove 2 pills from Bottle 2. (3) Remove 3 pills from Bottle 3. (4) Remove 4 pills from Bottle 4. (5) Combine the 10 pills and weight them together. (6) If Bottle 1 has the poisoned pills, the 10 pills will weigh 10.1 grams. (7) If Bottle 2 has the poisoned pills, the 10 pills will weigh 10.2 grams. (8) If Bottle 3 has the poisoned pills, the 10 pills will weigh 10.3 grams. (9) If Bottle 4 has the poisoned pills, the 10 pills will weigh 10.4 grams. And the problem is solved.

You are in a room with 2 doors -- one leads further into the dungeon, one leads to freedom. There are two guards in the room, one at each door. One always tells the truth. One always lies. What one question can you ask one of the guards that will help you pick the door to freedom?
Answer If you just wanted to determine which one tells the truth and which lies, you would ask: "If I were to ask the other guard whether you always tell the truth, what would he say?" A reply of "no" means you are talking to the truth teller, a reply of "yes" means you are talking to the liar. So since you only have one question to select the right door, you would have to ask "If I were to ask the other guard, which door would he say leads to freedom?" You would then select the door opposite the one he picked.

Here's one for the math wizards: Three companies agree to split the $1,000,000 cost associated with a toxic waste cleanup, as follows: 1) Company A agrees to pay four times the amount of Company B; 2) Company C agrees to pay one-fourth the sum of the amounts paid by Companies A and B. How much will each company pay? Answer Let x, y, and z be the amounts paid by Companies A, B, and C respectively. Since the total cost is $1,000,000, we know that x+y+z=1,000,000. From the other two conditions, we have x=4y and z=(x+y)/4 or equivalently, 4z=x+y. Substituting 4z for x+y into the first equation gives 4z+z=1,000,000, 5z=1,000,000 and z=200,000. Of the remaining 800,000 (x+y=800,000), substituting x=4y for x gives 5y=800,000, or y=160,000. Finally x=4y or $640,000. Thus, Company A pays $640,000, Company B pays $160,000 and Company C pays $200,000.

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Einstein's Riddle:
Einstein has been widely credited online with the following riddle, and with the claim that 98% of the world could not solve it. But several of our NIEHS scientists were able to solve it, and they said it is not all that hard if you pay attention and are very patient. Give it a try:

There are 5 houses in 5 different colors in a row. In each house lives a person with a different nationality. The 5 owners drink a certain type of beverage, smoke a certain brand of cigar, and keep a certain pet. No owners have the same pet, smoke the same brand of cigar, or drink the same beverage. Other facts:

1. The Brit lives in the red house.
2. The Swede keeps dogs as pets.
3. The Dane drinks tea.
4. The green house is on the immediate left of the white house.
5. The green house's owner drinks coffee.
6. The owner who smokes Pall Mall rears birds.
7. The owner of the yellow house smokes Dunhill.
8. The owner living in the center house drinks milk.
9. The Norwegian lives in the first house.
10. The owner who smokes Blends lives next to the one who keeps cats.
11. The owner who keeps the horse lives next to the one who smokes Dunhill.
12. The owner who smokes Bluemasters drinks beer.
13. The German smokes Prince.
14. The Norwegian lives next to the blue house.
15. The owner who smokes Blends lives next to the one who drinks water.

The question is : WHO OWNS THE FISH?
Answer Note: The suggested steps to the final answer below are not unique and are just one of several logical approaches that one could take to reach the proper solution. First consider color. The Norwegian lives in the first house (Fact 9), which is next to the blue house (fact 14). Thus, the second house is blue. The green house is to the left of the white house (Fact 4), which means that the green house must be either the third or fourth house. But the green house cannot be the third (center) house, because the owner of the center house drinks milk (Fact 8) and the owner of the green house drinks coffee (Fact 5). Thus, the fourth house is green and the fifth house is white. Since the Norwegian lives in the first house (Fact 9), and the Brit lives in the red house (Fact 1), the first house must be yellow, leaving the middle house red. Next consider drinks. The owner of the red (third) house is a Brit (Fact 1) who drinks milk (Fact 8). The owner of the green (fourth) house drinks coffee (Fact 5). The Norwegian lives in the yellow (first) house. The Dane drinks tea (Fact 3), and must be the owner of either the blue or white house. But he can't be the owner of the white house. If he were, then the beer-drinking Bluemaster smoker (Fact 12) would have to live in the blue house, making the Norwegian in the yellow house drink water. But that can't be right because........... the water drinker lives next to the owner who smokes Blends, not Bluemaster. Thus, the Dane must live in the blue house, and since the beer-drinking, Bluemasters smoker cannot live in the yellow house (because that owner smokes Dunhill), he must live in the white house, leaving the Norwegian in the yellow house drinking water. Next consider nationality. Only the German and Swede are unaccounted for. The German smokes Prince (Fact 13) and thus must live in the green house, since the owner of the white house smokes Bluemaster. Thus, the Swede must live in the white house. What about cigars? Only Blends and Pall Mall are unaccounted for. The Pall Mall smoker rears birds (Fact 6) and thus cannot live in the blue house, which has horses. Thus, the Pall Mall smoker lives in the red house and the Blends smoker in the blue house. Finally, what about pets? The horse and bird owners have been identified. The Swede keeps dogs as pets (Fact 2), which means dogs are pets in the white house. The Blends smoker lives next to the cat owner, which indicates that cats are the pet in the yellow house. And finally, the only pet left (although it is not even mentioned explicitly in the puzzle) is fish, which are the pets of the coffee-drinking, Prince-smoking German living in the green house. And the problem is solved.

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SEND + MORE = MONEY

Each letter in the above equation stands for a different number, and each time the same letter appears, it is the same number. What is the only set of numbers that makes this equation correct? This is a moderately hard one. Answer 9567 + 1085 = 10652

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Pronounced as one letter but written with three, two different letters there are and two only in me. I'm double, I'm single I'm black, blue, and gray. I'm read from both ends and the same either way.
Answer EYE

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What is it that when you take away the whole, you still have some left over?
Answer WHOLESOME

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We travel much,yet prisoners are, and close confined to boot. With the swiftest horse we keep pace, yet always go on foot.
Answer Spurs

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What is it that goes with an automobile and comes with it; is of no use to it,and yet the automobile cannot move without it?
Answer Noise

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You are a bus driver. At the first stop, 4 people get on. At the second stop, 8 people get on. At the third stop, 2 people get off, and at the last stop, everyone gets off. The question is: What color are the bus drivers eyes?
Answer Since the riddle starts out by saying you are the bus driver, the answer would be the color of your own eyes.

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You and a group of your friends are in the library. One friend says there is a $100 dollar bill hidden between pages 75 and 76 of a book in the library. But you decide not to go and look for it. Why?
Answer You know that the odd number in a book is ALWAYS on the right and the even number is ALWAYS on the left, so since the page numbers you were given could not be facing each other. Therefore, you know for a fact that the money could not be hidden there.

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Where did the other Dollar Go?
Three men check into a hotel, the manager charges them $30 for one room with three beds which they share. The men go to their room and settle in, after a few moments the manager realizes his mistake, he over charged the three men, the room rate was only $25. He sends for the bellhop to return the $5 to the three men. On his way to the room the bellhop realizes that he can't split $5 between 3 men so he decides to give each man $1 and pocket the remaining $2 as a tip. The bellman returns the $1 to each man. In the three mens minds they each paid $9 for the room, or a total of $27, include the $2 tip the bellhop kept and that equals $29, what happened to the other dollar?
Answer It's a trick on words that leads you to believe the answer is 30 and has you add the number 2 when you should be subtracting as follows: 3 x $9 = 27, then minus the $2 = $25 which is what they paid for the room. And if you take what they ultimately paid for the room ($25) and add the $3 ($1 each they received), and then add the $2 the bellhop took, you would reach the original $30 that was paid.

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Six glasses are in a row. The first three are full of juice; the second three are empty. By moving only one glass, can you arrange them so empty and full glasses alternate?
Answer Pour the juice from the 2nd glass into the 5th glass.

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You throw away the outside and cook the inside. Then you eat the outside and throw away the inside. What are you eating?
(speaking of throwing things away, don't miss our Reduce, Reuse, and Recycle tips!)
Answer An ear of corn.

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Why are 1990 American dollar bills worth more than 1989 American dollar bills?
Answer 1990 (1,990) dollar bills are worth $1,990; 1989 (1,989) dollar bills are worth $1,989.

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Rearrange the letters in the words "new door" to make one word.
Answer It can be respelled to read: One Word

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What is the largest amount of money in coins you can have without being able to make exact change for a dollar.
Answer $1.19 -- If you have three quarters, four dimes, and four pennies, you have $1.19, but you still cannot make exact change for a dollar.

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What number when multiplied against itself will result in a number which includes the numbers (1 - 9) in forward order, and then descending in order from the 9? (i.e., to get the number: 12,345,678,987,654,321)
Answer 111,111,111 X 111,111,111 = 12,345,678,987,654,321

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How many words (in the English language) can you think of that exactly rhyme with each of the words below. The blank boxes beneath each word can be used to type in your answers as you think of them.

Month	Orange	Silver	Purple
Answers Although debated frequently, most sources say that no word in the English language exactly rhymes with any of those words, but that depends on how strictly you want to interpret "rhyme". For example, some feel that sporange (the bag that contains spores in some types of mushrooms in the field of botany) rhymes with orange. But the popular "Ask Marilyn" column of the newspaper indicated that experts agreed that although the last syllable sounds very similar, neither of the two pronunciations given for sporange in Webster's Third New International Dictionary exactly rhyme with orange. Using www.yourdictionary.com pronunciations, circle may really rhyme with purple! But that wasn't the case for doorhinge/orange or all the other purple rhyming possibilities such as turtle/purple, hurdle/purple, and hurtle/purple.

Historical Teaser:
Where did the common "military salute" get its start?
Answer Armored knights raised their visors to identify themselves when they rode past their king. This custom has become the modern military salute.

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I am periodically the number 79. They once tried to make me from 29. If you add to me 80, I will appear to be 47 temporarily. What am I?
Answer Gold. On the PERIODIC table of elements, gold is represented by the number 79. Long ago alchemists tried to make it from copper (number 29). If mercury (number 80) comes into contact with gold, It will appear to be silver (number 47) for a while.
Learn more at the Lenntech Periodic Table

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What is the longest non-hyphenated word in English in which no letters are repeated (each letter appears only once)?
Answer UNCOPYRIGHTABLE (15 letters -- or UNCOPYRIGHTABLES, for 16-letters) There are several other long words you might have guessed such as DERMATOGLYPHIC (14 letters) and SUBDERMATOGLYPHIC (17 letters)

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What occurs once in a second, once in a minute, twice in a millennium, but never in the course of a lifetime?
Answer The letter "n".

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In the eyes, it causes blindness.
In the nose, it makes sneezes,
But some people seek it out,
And act as though it pleases.
Answer Smoke or smoking (Remember, smoking is very bad for you and those around you too!)

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What has no content, yet you can see it?
Answer A hole (or a shadow!)

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What is bigger when new and grows smaller with use?
Answer A pencil (or popsicle, sucker, lollipop, etc.)

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What do you use to "hoe a row, slay a foe, and wring with woe"?
Answer Your hands

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John Smith bought a used car for $600 and sold it to Mary Baker for $800. He later bought it back for $1000 and resold it for $1200. How much profit did John make?
Answer $400

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I am just a lowly thing, object of much derision,
I am odd because I multiply by division.
Answer An amoeba

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Sometimes it glitters, but often not;
May be cold, or may be hot.
Ever changing though the eye can't measure,
Concealed within may be many treasures.
Some find safety beneath its gate,
While some may die beneath its weight!
Old and broken, it brings forth life.
Answer A stone. Some stones shine while some don't. At noonday they are hot and at midnight cold. Stones are always getting smaller from wind, heat, and water, but eyes can't measure the change because it is so slow. And they hide things that men find valuable, such as gold and silver. Small creatures find safety beneath a stone, but a stone can also crush life. And when a stone is old and broken into tiny pieces, it becomes part of the soil that gives birth to trees and grass.

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What 3-letter word in English has an odd start, an even finish and an infinitely long middle?
Answer The word "vex." "v" is the Roman numeral for 5, which is odd. "x" is the Roman 10, which is even. "e" is the base of the natural logarithm. It is an irrational number (i.e., e = 2.718281828...) whose mantissa (part to the left of the decimal point) is infinitely long.

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I got it in a forest but didn't want it. Once I had it, I couldn't see it. The more I searched for it, the less I liked it. I took it home in my hand because I could not find it. What was it?
Answer A splinter

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Where can one stand up straight, but still be considered sideways?
Answer The equator. One would stand up straight with respect to the ground, but be somewhat sideways with respect to the Earth's axis.

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At night I come without being fetched. By day tho lost, I'm not really gone. What am I?
Answer A star

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Which word in the English language is most frequently spelled wrong?
Answer The word "wrong".

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Rearrange the letters in "OWONDER" to make one word.
Answer "ONE WORD"

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What runs fore to aft (i.e., front to back) on one side of a ship, and aft to fore (i.e., back to front) on the other side?
Answer The name of the ship

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Name one eight letter word that has kst in the middle, in the beginning, and at the end.
Answer "Inkstand" "in" is at the beginning, "kst" is in the middle, and "and" is at the end.

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"Think of words ending in -GRY. Angry and hungry are two of them. There are only three words in the English language. What is the third word? The word is something that everyone uses every day. If you have listened carefully, I have already told you what it is."
Answer "Language" is the third word no, it doesn't end in "gry". We didn't say the third word in "the English language" ends in -gry too. Of course, as in many brainteasers, proper punctuation (i.e., putting "the English language" in quotation marks) would have given the puzzle away.

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A clever thief in the olden days was charged with treason against the king and sentenced to death. But the king decided to be a little lenient so he let the thief choose his own way to die. What way should the thief choose?
Answer To die of old age.

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My host thinks I'm an irritation, a bother, a pain.
But he can't evict me, so I stay, remain.
Then one day I'm taken and ranked among my peers.
Can you guess just what I am? Then you might call me dear.
Answer A pearl.

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I can make you lighter, or cause your death. Some are afraid of me, but I'm also loved by many.
Answer Water

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There is a common English word that is seven letters long. Each time you remove a letter from it, it still remains a common English word -- from seven letters right on down to a single letter. What is the original word, and what are the words that it becomes after removing a letter at a time?
Answer The word "snowing." It decomposes down to "sowing", "swing", "sing", "sin", "in", and "I".

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What falls but never breaks?
Answer Night,

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What breaks but never falls?
Answer Day

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Part carbon, part water,
I am poison to the fishes.
Many falsely claim my name,
I am the pause that refreshes.
Answer Soda

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An egg salesman was asked how many eggs he had sold that day. He replied, "My first customer said, 'I'll buy half your eggs and half an egg more'. My second and third said the same thing. When I had filled all three orders, I sold out of eggs without having to break a single egg the whole day." How many eggs were sold in all? Explain this!
Answer Seven. He sold 4 eggs to the first customer (half of seven is 3 1/2 plus the other half = 4 eggs) 2 to the second person (half of the remaining 3 eggs = 1 1/2, plus the other half = 2) and 1 to the third (half of the remaining egg, plus the other half = 1).

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It can be cut and will grow back. Yet when you least expect it, it may disappear never to return.
Answer Hair

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I'll lap at your heels,
If you give me the chance.
Though I won't fetch or stay,
I surely will dance.
Answer Fire

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You can see it, but you can't touch it. It may disappear, but has never really left you. It grows throughout the day. What is it?
Answer Your shadow

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Hi! Ma and Pa told me I'd better say that all the two-letter words in this paragraph have something in common ...... or else! What's the common factor here?
Answer All the two-letter words are abbreviations of U.S. states (Hawaii=HI, Massachusetts=MA, Pennsylvania=PA, Maine=ME, Idaho=ID, Indiana=IN and Oregon=OR).

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You are taking a vacation on an island in the middle of a lake. The lake is in a remote part of Maine and there has never been a bridge connecting the island to the land. Every day a tractor and wagon gives hay rides around the island to all the children. Puzzled as to how the tractor had gotten onto the island, you ask around and find out that the tractor was not transported to the island by boat or by air. Nor was it built on the island. Explain how`t(e tractor may have gotten there?
Answer It was driven over in winter when the lake was frozen over.

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There is a barrel with no lid and some rum in it. "This barrel of rum is more than half full," said Charlie. "No it's not," say Harry. "It's less than half full." Without any measuring implements and without removing any rum from the barrel, how can they easily determine who is correct?
Answer Tilt the barrel until the rum barely touches the lip of the barrel If the bottom of the barrel is visible, then it is less than half full. If the bottom is still completely covered by the rum, then it is more than half full.

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What two words in the English language uses all five vowels plus Y in alphabetical order and uses each one only once?
Answer "Facetiously" (which means "in a comical, jocular or flippant manner") and abstemiously (which means "eating and drinking moderately, or using only the bare necessities")

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By Moon or by Sun, I shall be found; yet I am undone when there's no light around.
Answer A shadow

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The more you have of it, the less you see. What is it?
Answer Darkness

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Only one color, but not one size,
Stuck at the bottom, yet easily flies.
Present in sun, but not in rain,
Doing no harm, and feeling no pain.
Answer A shadow

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Forward I am heavy, but backward I am not. What am I?
Answer The word 'ton'.

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It is in a rock but not in stone,
It is in marrow but not in bone.
It is in a bolster but not in bed.
It's not in the living, and not in the dead.
Answer The letter "r".

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What is nothing, yet has a name? It is sometimes tall and sometimes short. It joins our talks and joins our games, And plays in every sport.
Answer A shadow

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I know a word of letters three. Add one letter to it and none there will be. What is the word?
Answer The word "one." Add an "n" and then you have "none."

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What is it that has four legs, one head and a foot?
Answer A bed

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I weaken all men for hours each day. I show you strange visions while you are away. I take you by night, by day take you back, None suffer to have me, but do from my lack.
Answer Sleep

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They have not flesh nor feathers, nor scales nor bone; but they do have fingers and thumbs of their own.
Answer Gloves

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Many things can create one. It can be of any shape or size. It is created for various reasons, and it can shrink or grow with time. What is it?
Answer A hole

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This is an unusual paragraph. I'm curious how quickly you can find out what is so unusual about it? It looks so plain you would think nothing was wrong with it! In fact, nothing is wrong with it! It is unusual though. Study it, and think about it, but you still may not find anything odd. But if you work at it a bit, you might find out! Try to do so without any coaching!
Answer The letter e, which is the most common letter in the English language, does not ever appear in the paragraph.

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Even Einstein didn't know everything -- so if you're having trouble understanding something on our website, or if you have a funny science joke, riddle, or brainteaser to share, let us know. But first, familiarize yourself with our Privacy Policies and other Disclaimers, which restrict our use of any information we receive from you. And be sure to ask permission from your parent or guardian! You should always get permission from your parents or guardian before providing any information through the internet or by e-mail.

The most important feature to recognize in solving this puzzle is that Postman A needed to know that Postman B did not have twins in order to solve the puzzle. That means that there must be two possible solutions that satisfied the "age in years" and "number of windows" conditions of the problem. He needed to rule out twins to solve the problem. To summarize, there must have been two potential solutions with 3 son's ages having:

(i) equal products (the age condition)

(ii) equal sums (the windows condition)

(iii) one involving twins and one not.

If you really wanted to be fussy, since a house cannot have a fraction of a window, it also means that the ages of the sons must all be in integers (whole numbers) and not involve fractional ages.

The one solution to the problem that satisfies all of these conditions is (1, 5, 8) which has the same sum (14) and the same product (40) as another possible solution involving twins (2, 2, 10). There is just no other solution that works involving a postman's age less than 90 years old. That is, another solution that works mathematically is 2-5-9 and 3-3-10, but that would make the postman 90 years old.

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